does the 'mesh' mean this was done with some sort of scanning then reproduction ?
I designed them in Discreet Plasma and made the G-code with Vectric Cut3D
Discreet's Plasma software is/was a 3D application. Vectic's Cut3D will take these models (A.K.A. "meshes") that were created in Plasma, and create G-code to manufacture them.
You could indeed "scan" some blades and make replicas that way. You could also use a digitizing probe and again make replicas. If you model them yourself, the design options are limitless.
Would you form the root of the blade whilst it was still in a block of wood form then clamp the root in your 4th axis
A 4th axis is not required, and was not used, as you can see from his video.